Fix unhelpful error when no stress packages are found (#6798)

Co-authored-by: Ben Broderick Phillips <bebroder@microsoft.com>

eng/common/scripts/stress-testing/find-all-stress-packages.ps1

@@ -31,8 +31,10 @@ function FindStressPackages(
     $filters['stressTest'] = 'true'
     $packages = @()
     $chartFiles = Get-ChildItem -Recurse -Filter 'Chart.yaml' $directory
-    Write-Host "Found chart files:"
-    Write-Host ($chartFiles -join "`n")
+    if ($chartFiles) {
+        Write-Host "Found chart files:"
+        Write-Host ($chartFiles -join "`n")
+    }
 
     if (!$MatrixFileName) {
         $MatrixFileName = 'scenarios-matrix.yaml'

eng/common/scripts/stress-testing/stress-test-deployment-lib.ps1

@@ -172,6 +172,10 @@ function DeployStressTests(
                 -MatrixFilters $MatrixFilters `
                 -MatrixReplace $MatrixReplace `
                 -MatrixNonSparseParameters $MatrixNonSparseParameters)
+    if (!$pkgs -or !$pkgs.Length) {
+        Write-Warning "No stress test packages found in $searchDirectory"
+        exit 0
+    }
     Write-Host "" "Found $($pkgs.Length) stress test packages:"
     Write-Host $pkgs.Directory ""
     foreach ($pkg in $pkgs) {